Custom Validations for ASP .Net Web page

Question

Hi All,

I have webpage with the following fields

EmpID- Allow only numeric
Name-Allow only Characters 
Department-Allow only with in the list(DropDownList)
Designation-Allow only characters
Phone-In the format of "99999 99999"
EmailID- In the format of [email protected]

Here,
Except Phone remaining fields are mandatory.

So i need to validate this page before submitting it..
Can any body suggest me how can i put custom validation for this?